Asymmetrical thioureas, such as those described in U.S. Pat. No. 4,097,605 to Fancher, have required 2 or more reactions and isolation steps to produce. Fancher teaches the use of an intermediate isolated isothiocyanate which, when reacted with a properly selected amine, produces an asymmetrical thiourea.
Hodgkins et al., J. Am. Chem. Soc., 83, 2532 (1961) teach the production and isolation of an isothiocyanate by reaction of an amine, CS.sub.2 and base followed by reaction with ethyl chlorocarbonate. Takami et al., Chem. Pharm. Bull. (Japan), 21, 1311 (1973) teach the reversable formation of an isothiocyanate by the decomposition of a dithiocarbamic acid salt. None of these methods teach the production of asymmetrical thioureas.